It is quite common in present day aircraft designs to place the engine nacelle below the wing with the inlet of the nacelle being positioned forwardly of the leading edge of the wing. The design of modern, efficient transport aircraft has increasingly led to the use of high-bypass ratio engines which are considerably larger in diameter than equivalent low-bypass engines, but are highly desirable because of their significantly lower fuel consumption and reduced noise level. Because of the practical limits on landing gear length and runway clearance, designers of new jet transport designs increasingly require much closer coupling of these larger engines to the wing than was practiced in the previous generation of transport designs. Such close mounting of the engines presents interrelated problems and has certain shortcomings.
For example, the close coupling of such engines has a tendency to interfere with airflow over the wing, specifically in the landing and takeoff mode where the aircraft is generally operating at a relatively high angle of attack. This results in increased interaction of the engine nacelle and the wing flow fields, which can degrade airplane performance.
Also, in the thrust reverse mode of operation, fan reverse flow must exit forward of the wing to avoid the tendancy for it to lift the airplane, and reversal or blocking of primary flow is discouraged. The struts by which the engine is mounted to the wing must therefore be long and shallow, and accordingly heavy in order to have adequate stiffness. Further, with minimum ground clearance, there is a greater problem with conjestion and particularly re-injestion of reverse thrust flow. Thrust reverse must be shut off at fairly high speeds, putting additional burden on the brakes and tires in addition to the burden caused by not reversing primary flow.
Another consideration is to have the cowl of the engine arranged so that there is convenient access to the engine. In many engine designs, access is provided by incorporating hinged panels, access holes, latches, etc., and these can unnecessarily add weight to the engine.
In view of the above, it is an object of the present invention to provide an engine installation which has a desirable balance of features relative to the considerations noted above.